Microstructural Analysis Research Articles

Improving the weathering properties of heat-treated wood by acetylation

Abstract Heat-treated wood is widely used for outdoor furniture manufacturing. However, it is susceptible to against physical degradation such as cracking and discoloration. This study involved heat-treated wood at three different temperatures of 180 °C, 200 °C and 220 °C was acetylated using vacuum-pressure impregnation methods to enhance photostability, dimensional and thermal stability. The laboratory chromaticity data indicated a substantial enhancement of the photostability of the acetylated heat-treated wood. The color difference was reduced from 11.89 to 10.08 for the 180 °C treatment, then from 10.24 to 9.02 for the 200 °C treatment, and from 8.31 to 8.11 for the 220 °C treatment compared to unmodified wood at the same temperature. The microstructure analysis and chemical composition study suggested that the hydroxyl groups were greatly reduced, rendering the microstructure and chemical composition of wood relatively stable. In addition, the results of water contact angle, water absorption, swelling and shrinking data show that acetylated wood exhibits lower hydrophilicity and greater dimensional stability. Thermo-gravimetric analysis reveals that acetylated wood maintained better thermal stability, as evidenced by the greater maximum temperature for thermal degradation. The weathering resistance of heat-treated wood was significantly improved by acetylation treatment.

Developing an activated biochar-mineral supplement for reducing methane formation in anaerobic fermentation

Abstract The effects of biochar on methane emissions from soils are well understood. However, biochar effects on methane production from livestock have received less attention. In this study, a biochar-mineral supplement for livestock was developed by pyrolyzing a mixture of wheat straw, aluminosilicates, iron sulfate, and zinc oxide at 600 ℃. The supplement was then activated using peracetic and propionic acids, and potassium nitrate. The activated biochar-mineral supplement was characterized using analytical techniques. A high surface area, a high concentration of oxygen-containing functional groups, and a high concentration of free radicals, associated with O and Fe unpaired electrons, assisted the supplement with catalysing the oxidation of methane. Microstructural analysis of the supplement suggested the formation of organo-mineral phases, rich in C, O, Fe, Si, Al, K and Ca, indicating that the biochar reacted with mineral additives to preserve them. To assess the potential of the supplement to reduce methane produced form livestock, an in vitro batch culture incubation was conducted (n = 3) with rumen fluid sourced from Holstein–Friesian steers. The supplement was incubated at inclusion rates of 0% (control), 1.5%, 4.0% and 6.0% of dry matter (DM), with a Rhodes grass hay substrate. Compared to the control, the supplement reduced cumulative gas production by 10.1% and 12.7% and methane production by 19.03% and 29.32% after 48 h when included at 4.0% and 6.0% DM (P < 0.05), respectively, without causing any detrimental impacts on fermentation parameters. The supplement assisted with reducing the concentration of dissolved mineral nutrients, such as P and Mg, when included at 4.0% and 6.0% DM (P < 0.05). Graphical abstract

Role of Calcined-Clay-Based Geopolymers for Effective Stabilization of Expansive Soils

Effective stabilization of expansive soils remains a challenge for transportation infrastructure. In line with the United Nations' sustainability goals, most research on eco-friendly stabilizers is still in its early stages, focusing primarily on laboratory evaluations. This study aims to evaluate the efficacy of alkali-activated calcined clay-based geopolymers (CCBGPs) and investigate the most effective minerals contributing to its stabilization of expansive soils. Four locally available clays were used to synthesize CCBGPs, and based on unconfined compressive strength, two of them were selected for further stabilization of expansive soils. The treated soils underwent comprehensive engineering, microstructural, and mineralogical analyses. A machine learning (ML)-based regression model was developed and tested to examine the effects of CCBGP and soil mineralogy on engineering performance of the treated soils. Engineering tests on treated specimens showed improved performance with increasing CCBGP dosage and curing periods, while microstructural and mineralogical analyses revealed physical and chemical interactions with soil particles that enhanced engineering properties. The ML model identified kaolinite as the most influential factor, which enhanced geopolymerization by forming more binder gel, and improved engineering properties. Overall, the research indicated that selection of kaolinite-rich, locally available CCBGPs could serve as sustainable source for improving expansive soils in transportation infrastructure.

Performance, mechanisms of recycled aggregate modified with alkaline activated geopolymer and its characteristic of ITZ with asphalt

ABSTRACT The alkaline activated geopolymer was utilised to enhance the performance of recycled aggregate (RA) by repairing voids and cracks, thereby meeting the requirements for aggregates in asphalt mixtures. This treatment significantly improved the physical properties of RA, specifically by reducing water absorption, crushing value, and Los Angeles (LA) abrasion value, ensuring compliance with relevant specifications. Microstructural analysis (XRD, TG, SEM, and EDS) revealed that geopolymer treatment could transform Ca(OH)2 in cement mortar into C–S-H and C-A-H phases, while also forming N-A-S-H gel. These transformations strengthened the interfacial transition zone (ITZ) surrounding the RA, thereby enhancing the crack resistance and fatigue durability of asphalt mixtures. Consequently, this method demonstrated significant potential for the effective utilisation of RA in asphalt mixtures.

Thermal, Mechanical, and Microstructural Properties of Novel Light Expanded Clay Aggregate (LECA)-Based Geopolymer Concretes

The construction sector’s reliance on traditional cement significantly contributes to CO2 emissions, underscoring the urgent need for sustainable alternatives. This study investigates fine (0–4 mm), rounded, uncoated, porous-surfaced lightweight expanded clay aggregate (LECA)-based geopolymers, which combine the low-carbon benefits of geopolymers with LECA’s lightweight and insulating properties. Geopolymers were synthesized using lignite-rich fly ash with varying ratios of LECA to aggregate. Mechanical testing revealed that the reference mixture without LECA (REF-GEO) achieved the highest compressive strength of 37.89 ± 0.75 MPa and flexural strength of 7.62 ± 0.11 MPa, while complete substitution of the aggregate with LECA (LECA-100%) reduced the compressive strength to 17.31 ± 0.88 MPa and flexural strength to 3.41 ± 0.11 MPa. The density of the samples decreased from 2.06 g/cm3 for REF-GEO to 1.31 g/cm3 for LECA-100%, and thermal conductivity dropped significantly from 1.15 ± 0.07 W/mK to 0.38 ± 0.01 W/mK. Microstructural analysis using XRD and SEM-EDX highlighted changes in the material’s internal structure and the increase in porosity with higher LECA content. Water vapor permeability increases over time, particularly in samples with higher LECA content. These findings suggest that LECA-based geopolymers are suitable for low-load or non-structural elements. They are ideal for sustainable, energy-efficient construction that requires lightweight, insulating, and breathable materials.

Effects of Graphene Nanoplatelets and Nanosized Al4C3 Formation on the Wear Properties of Hot Extruded Al-Based Nanocomposites

This study investigates the influence of graphene nanoplatelets (GNPs) and the formation of nanosized Al4C3 on the tribological performance of hot extruded aluminum-based nanocomposites. Al/GNP nanocomposites with varying GNP contents (0, 0.1, 0.5, and 1.1 wt.%) were fabricated through powder metallurgy, including ball milling, compaction, and hot extrusion at 500 °C, which was designed to facilitate the formation of nanosized carbides during the extrusion process. The effect of GNPs and nanosized carbides on the tribological properties of the composites was evaluated using dry friction pin-on-disk tests to assess wear resistance and the coefficient of friction (COF). Microstructural analyses using scanning electron microscopy and energy-dispersive X-ray spectroscopy confirmed the uniform distribution of GNPs and the formation of nanosized Al4C3 in the samples. Incorporating 0.1 wt.% GNPs resulted in the lowest wear mass loss (1.40 mg) while maintaining a stable COF (0.52), attributed to enhanced lubrication and load transfer. Although a higher GNP content (1.1 wt.%) resulted in increased wear due to agglomeration, the nanocomposite still demonstrated superior wear resistance compared to the unreinforced aluminum matrix. These findings underscore the potential of combining nanotechnology with precise processing techniques to enhance the wear and friction properties of aluminum-based composites.

Sustainable Geopolymer Tuff Composites Utilizing Iron Powder Waste: Rheological and Mechanical Performance Evaluation

Geopolymers are a sustainable alternative to Portland cement, with the potential to significantly reduce the carbon footprint of conventional cement production. This study investigates the valorization of industrial waste iron powder (IP) as a fine filler in geopolymers synthesized from volcanic tuff (VTF). Composites were prepared with IP substitutions of 5%, 10%, and 20% by weight, using sodium hydroxide and sodium silicate as alkaline activators. Microstructural and phase analyses were conducted using scanning electron microscope coupled with energy dispersive X-ray spectroscopy (SEM-EDS), X-ray fluorescence (XRF), X-ray diffraction (XRD), and differential scanning calorimetry (DSC), while rheological properties, compressive strength, and flexural strength were assessed. The impact of curing temperatures (25 °C and 80 °C) on mechanical performance was evaluated. Results revealed that air content increased to 3.5% with 20% IP substitution, accompanied by a slight rise in flow time (0.8–2 s). Compressive and flexural strengths at 25 °C decreased by up to 22.48% and 28.39%, respectively. Elevated curing at 80 °C further reduced compressive and flexural strengths by an average of 45.30% and 64.68%, highlighting the adverse effects of higher temperatures. Although these formulations are not suitable for load-bearing applications, the findings suggest potential for non-structural uses, such as pavement base layers, aligning with sustainable construction principles by repurposing industrial waste and reducing reliance on energy-intensive cement production.

Mechanical characterization of sandwich composite structures with Alumix231 foam core between Al2024/B4C composite plates

Abstract The study investigates the production of lightweight B4C particle-reinforced aluminum sandwich foam (ASF) materials, crucial for high impact and corrosion resistance, particularly in defense and automotive sectors. These materials are manufactured via powder metallurgy. Five different combinations of ASF materials, layered and unlayered with B4C, were examined. Alumix231 served as the primary material in the Al foam, with TiH2 as the blowing agent. In layered ASF materials, Al2024 powder acted as the main material, reinforced by B4C particles. Samples with various configurations, including foam, foam/Al2024 layers, and 5-10–20 % B4C particle-reinforced Al2024 layers, were produced. After powder mixing, they were filled into a hot pressing mold, pre-pressed at 25 MPa, dwelled at 550 °C for 30 min, then hot pressed at 200 MPa to form foamable preform material. B4C particle-layered ASF materials were generated by foaming the preforms in a steel mold at 750 °C for 11 min. Microstructure, density, pore size, and morphology analyses were conducted. Al2024 exhibited the highest density at 99 %, decreasing with increased B4C ratio. With more B4C, compressibility decreased, and agglomeration increased. Pores were observed around TiH2 and Si particles in B4C-lacking materials. The material with the best homogeneity and spherical pore resemblance was noted as Alumix231.

STUDY THE EFFECT OF ZIRCONIUM, NICKEL AND HEAT-TREATMENTS ON THE MICROSTRUCTURE AND MECHANICAL PROPERTIES OF COLD-ROLLED AA6111 ALLOY

The cold rolling effect on the microstructure and mechanical properties of recycled AA6111 alloy with Zr or/and Ni were investigated. All alloys were produced by the stir-casting method. homogenization heat treatment (500 ºC for 6 hours) was performed on AA6111 alloy only. The alloys were solutionized (at 540 ºC for 30 minute) and artificially aged (at 180 ºC for 10 hours). The optical micrograph, scanning-electron microscope (SEM) and X-ray Diffraction (XRD) studies for all samples. The microstructure analysis displayed different fine intermetallic phases distributed in large amounts in alloys containing Zr or/and nickel compared to AA6111 alloy. The combined alloying elements' addition effect with the cold rolling effect and artificial aging led to great improvements in the mechanical properties, where the hardness and tensile properties of all alloys increased. The AA6111+0.41wt%Ni alloy showed the highest hardness value, as it increased to 161 HV after artificial aging, while the AA6111+0.54wt%Zr alloy showed the highest YS and UTS, which increased to 252 MPa and 342 MPa, respectively.

Microstructure, XRD characteristics and tribological behavior of SiC–graphite reinforced Cu-matrix hybrid composites

Abstract This study’s main goal is to investigate how the properties of pure copper are impacted by the addition of silicon carbide–graphite reinforcement. Here in this research a powder metallurgy procedure is used to make copper matrix composites with different amounts of silicon carbide–graphite reinforcement (2 %, 5 %, 8 %, and 10 %) by weight. The microstructure, phases present, wear analysis, and X-ray diffraction analysis were all thoroughly examined, while scanning electron microscopy was used for imaging the microstructure of materials. The absence of any intermediate phases between the reinforcing materials and the copper matrix, according to X-ray diffraction data, suggests a strong interfacial interaction between them. A microstructural analysis of the copper matrix indicated a consistent dispersion of silicon carbide–graphite. The amount of reinforcement employed was found to have an impact on the wear characteristics of these copper matrix composites. Notably, the softness of graphite caused the hardness to drop when it was added. The 5 % reinforcement composite material outperformed the other evaluated composite materials in terms of wear rate, which was calculated in term of specific wear rate by using a pin-on-disc testing machine. This implies that this specific composite could be useful for tribological applications.

Cortical structural degeneration and functional network connectivity changes in patients with subcortical vascular cognitive impairment.

To explore the structural basis of functional network connectivity (FNC) changes and early cortical degenerative patterns in subcortical vascular cognitive impairment (SVCI). We prospectively included SVCI cases and healthy controls (HCs). FNC alterations were evaluated using group-independent component analysis of resting-state functional MRI data. Cortical microstructural and macrostructural alterations were assessed using gray matter-based spatial statistics analysis with neurite orientation dispersion and density imaging and cortical thickness analysis with FreeSurfer software on T1-weighted images, respectively. Spearman correlation analyses were performed to assess relationships between FNC alterations and cortical microstructural/macrostructural alterations and between FNC, cortical thickness, or neurite density index (NDI)/orientation dispersion index (ODI) alterations and cognitive performance. Forty-six SVCI patients and 73 HCs were recruited. FNC analysis showed lower network connectivity between the visual network (VN) and sensorimotor network (SMN) in SVCI, positively correlated with information processing speed (p=0.008) and negatively with summary SVD score (p = 0.037). Cortical microstructural analyses exhibited a lower NDI, mainly in the VN and default mode network (DMN) areas (PFWE < 0.05, cluster > 100 voxels), and lower ODI, mainly in the SMN and DMN areas (PFWE < 0.05, cluster > 100 voxels) in SVCI, both of which were related to cognitive function (p < 0.05). However, cortical thickness did not differ between groups. Lower NDI in the lateral occipital cortex was linked to lower VN-SMN connectivity in SVCI (p = 0.002). Cortical microstructural alterations may serve as the basis for FNC changes in SVCI.

Fatigue behavior of friction stir welded AA6061 alloy using brass insert

Aluminum alloys, broadly used in aerospace and automotive, are particularly susceptible to fatigue failures. The grain refinement characteristics can improve the fatigue behavior of aluminum alloys, which can be achieved using friction stir welding (FSW). The primary aim of this study is to examine how incorporating a brass insert influences the fatigue crack growth behavior of AA6061-T6 alloy welded through FSW, comparing welds with and without the insert. Microstructural analysis showed fine recrystallized grains are obtained for both welds. However, welding with the insert exhibited smaller grains. Moreover, robust intermetallics are formed for welding with insert due to the intermixing reaction at FSW temperature, which improves mechanical properties such as hardness and tensile strength. The findings on fatigue indicate that the fatigue resistance of the weld with insert is significantly high, which can be attributed to the increased grain boundaries and development of strong intermetallic compounds, which hindered the crack propagation. Fractographic analysis of the fracture surfaces indicated the presence of striation marks in the weld with the insert, which slowed crack propagation and prolonged fatigue life. The findings suggest real-world applications in industries, where improving the fatigue life and structural reliability of welded aluminum components is critical.

Sleep microstructure in patients with systemic sclerosis: A cyclic alternating pattern analysis study.

The cyclic alternating pattern (CAP) is a cyclic variation of sleep electroencephalogram activity within non-rapid eye movement (non-REM) sleep and increased CAP is the marker of sleep instability. The present study aimed to examine the expression of cyclic alternating pattern in non-REM sleep in patients with systemic sclerosis (SSc) and to compare these findings with the control group. Thirty-one patients with SSc were compared with matched controls by age, gender, body mass index, and apnea-hypopnea index (AHI). Sleep measurements were obtained by standard polysomnography with conventional sleep scoring. A CAP analysis was performed and verified by certified somnologists. The sleep parameters of the SSc and control groups were similar for sleep efficiency, sleep stage percents N1, N2, N3, sleep latency, and minimum oxygen saturation (p = 0.627, p = 0.693, p = 0.530, p = 0.736, p = 0.772, and p = 0.693, respectively). The SSc patients presented a higher arousal and periodic limb movement index. The CAP analyses showed that SSc patients had higher CAP numbers, phase A2 index, A3 duration, and lower A1 duration (p = 0.032, p = 0.016, p = 0.016, and p = 0.016, respectively). Overall the phase A2 index, A2 total time during non-REM sleep were significantly higher and the A1 duration was significantly lower in SSc patients, although sleep efficiency and the distribution of sleep macro-structure seem to be similar to the control group. This study emphasises that microstructure analysis performed with CAP provides information that would otherwise be lost if only macrostructure analysis were considered.

Intrinsic Mechanisms of Differences in Wetting-Induced Deformation of Soils on Chinese Loess Plateau: Insights into Land Stability and Sustainable Management

Wetting-induced soil deformation significantly impacts land stability and management on the Chinese Loess Plateau. This study analyzed silt soils from the Late Pleistocene (1 m depth) and Middle Pleistocene (25 m depth) to investigate compression and collapsible deformation during wetting. The compression in both soils progressed through three stages: slow deformation under low pressure, accelerated deformation under moderate pressure, and decelerated deformation under high pressure. Wetting intensified the compression in the 1 m sample but reduced it in the 25 m sample, with the deformation becoming more sensitive to the initial water content under higher pressures. Collapse tests showed contrasting behaviors: the 1 m sample exhibited collapsibility, while the 25 m sample displayed expansiveness (a negative collapsibility coefficient). Microstructural analysis revealed that the 1 m sample with abundant macropores and overhead structures had a lower structural stability than the 25 sample with more stable, rounded micropores. The wetting-induced deformation was governed by the balance between clay mineral expansion and structural collapse, with collapsibility prevailing when collapse dominated and expansiveness prevailing when expansion was predominant. These findings provide valuable insights into soil–water interactions and support improved land use and management strategies in the loess region.

Effects of Rubber Particle Size and Substitution Rate on the Behavior of Eco-Friendly Rubberized Concrete

One of the world's largest tire graveyards is located in the Al-Salmi area of Kuwait, where over 42 million discarded waste rubber tires have been accumulated over a time period of 17 years. This study aims to develop sustainable, cost-effective building materials for the construction industry, utilizing waste rubber as a partial substitute for fine and coarse aggregates in concrete mixtures. Three types of untreated rubber particles were used: powder rubber (P) with a diameter between 0.4 and 0.6 mm, crumb rubber (CR) with a diameter between 0.6 and 2 mm, and 2.6 and 3.5 mm respectively, and rubber chips (CH) with a diameter ranging between 2 and 18 mm. Fine aggregates were replaced by P and CR, while coarse aggregates were replaced by CH, at a substitution rate of 10 and 20% by volume. The impact of rubber particles on workability was assessed on fresh rubberized concrete, while the compressive strength was evaluated at 7, 14, and 28 days. Microstructural analysis using Scanning Electron Microscopy (SEM) was also conducted to collate the macroscopic behavior with internal structural changes. The results showed that increasing the rubber content and particle size led to reductions in workability and compressive strength. Large rubber particles, particularly chips, caused gaps and microcracks in the matrix, exhibiting poor adhesion at the Interfacial Transition Zone (ITZ). These findings demonstrate the potential of rubberized concrete as an eco-friendly alternative, with optimization needed for practical applications.

Deformation mechanisms of high strength and plasticity Fe-24Mn-3.5Cr-0.4C austenitic steel at 4.2 K

In this work, austenitic high-Mn steel that exhibits both high strength and plasticity at extremely low temperatures was designed and investigated, which demonstrates a yield strength of 1022 MPa, a tensile strength of 1532 MPa, and an elongation of 25% at 4.2 K, and enables potential operating in low-temperature structural materials. Compared to at room temperature, both the yield strength and the tensile strength of the high-Mn steel at low temperature increased, while the elongation at break decreased. A comparative study of its microstructural evolution was carried out using X-ray diffraction, transmission electron microscopy, and electron backscatter diffraction. The microstructure analysis revealed that the dislocations and nano-twinning control the strain-hardening behavior of the twinning-induced plasticity behavior of the Fe-24Mn-3.5Cr-0.4C steel.

Effect of keyhole and lack-of-fusion pores on the anisotropic microstructure and mechanical properties of PBF-LB/M-produced CuCrZr alloy

Abstract Due to the high reflectance and heat conductivity of copper and its alloys, the processing window for laser-based powder bed fusion (PBF-LB/M) processing of high-density copper components fundamentally overlaps with conduction and keyhole melting zones, resulting in the emergence of certain pores in the structure of printed parts. The present research aims to study how the development of process-induced lack-of-fusion or keyhole porosities during the PBF-LB/M process can affect the anisotropic microstructure and mechanical properties of the produced copper alloys. For this purpose, several samples were produced utilizing a similar CuCrZr-feedstock composition but varied process parameters from different areas of the PBF-LB/M processing window, specifically at laser powers of 300 W and 380 W which define the boarders of the conduction and keyhole regimes. X-ray computed tomography (XCT) revealed that the 300-W and 380-W samples achieved relative densities of 98.88% and 99.99%, respectively, with elongated lack-of-fusion pores forming at 300 W and semi-spherical keyhole pores at 380 W. Microstructural analyses employing scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD) demonstrated strong anisotropy in different build directions of the samples, owing to the growth of long columnar grains with intense &lt; 101 &gt; orientation along the build directions. Here, the emergence of different types of pores can cause competition between the epitaxial growth of columnar grains and the heterogeneous nucleation of new grains on the layers’ interfaces, thereby significantly varying the grain size, preferred orientation, crystallographic texture, and microstructural anisotropy of the samples. Furthermore, compression tests and nanoindentation measurements of the printed alloys in the longitudinal and transverse directions revealed that the 300 W and 380 W samples exhibited compressive strength anisotropies of 0.061 and 0.072, and average nanoindentation hardness values of 1.3 GPa and 1.5 GPa, respectively. The orientation of elongated lack-of-fusion porosities perpendicular to the loading axis was identified as the most damaging factor, significantly reducing mechanical performance compared to the uniformly distributed keyhole pores.

Solubilization effects of egg yolk granules induced by weakly alkaline treatment.

Egg yolk granules (EYGs) are water-insoluble components of egg yolk that are rich in protein and phospholipids. Improving the solubility of EYGs is crucial for their development and utilization. The solubilization of EYGs in a weak alkaline environment (pH7.5-8.5) was investigated through physicochemical properties, microstructure analysis, and metabolomics. The results reveal a significant reduction in the average particle size of EYGs, ranging from 70.49 to 91.28nm in weakly alkaline conditions. Microstructure and spectroscopic analyses indicate conformational changes in EYGs under these conditions, facilitating the solubilization of proteins, calcium, phosphorus and other components. Furthermore, metabolomics analyses confirms that depolymerization of EYGs promotes the release of glycerophospholipids. These findings underscore the beneficial effects of weakly alkaline conditions on the solubility of EYGs.

Gluten protein transformations during bread processing: Molecular and microstructural analysis

Gluten protein transformations during bread processing: Molecular and microstructural analysis

Modification study of underwater epoxy-cement mortar with polyacrylate latex: Engineering performance optimization and microstructure analysis

Modification study of underwater epoxy-cement mortar with polyacrylate latex: Engineering performance optimization and microstructure analysis